Step 1

Cut the sweet potatoes into bite-sized pieces about 1/2-inch around.

Step 2

Prepare the sauce: In another bowl, combine the vinegar, soy sauce, hoisin sauce, sesame oil, chili oil, sugar, and Sichuan pepper. Stir until the sugar is dissolved and set aside.

Step 3

You may need to turn on your stove’s exhaust fan, because stir-frying dried chilis on high heat can get a little smoky. Heat a wok or large skillet over high heat until a bead of water sizzles and evaporates on contact. Add 1 tablespoon of the peanut oil and swirl to coat the base. Add the chilis and stir-fry for about 30 seconds, until the chilis have just begun to blacken and the oil is slightly fragrant. Add the sweet potatoes and stir-fry for 5 to 6 minutes, continuously stirring, until the outsides are golden brown.

Step 4

By now the sweet potatoes should be golden brown on the outside, and the pan a little dry. Create a well in the middle of the pan and pour in the remaining 1 tablespoon of peanut oil. Add the scallion whites, garlic, and ginger, and stir-fry for 30 seconds. Pour in the sauce and mix to coat the other ingredients. Allow the mixture to simmer for 1 to 2 minutes to thicken. Stir in the peanuts or cashews and cook for another 1 minute. Transfer to a serving plate, sprinkle the scallion greens on top, and serve.